The present invention relates to a dual-polarization microwave lens, that is, a lens capable of operating with two crossed polarizations. The present invention also relates to the application of such a lens to the construction of a phased-array antenna.
For implementing a phased-array antenna, for instance, it is known to use a microwave lens made up of panels introducing a phase shift of the electromagnetic microwave passing through them. Each of these panels includes wires carrying diodes, parallel to one another. Controlling the ON or OFF state of the diodes allows varying of the phase shift imparted to the incident wave and, as a result, obtaining an "electronic" scanning. Such an antenna is, for example, described in the French patent No. 2,469,808. Its principle is illustrated in FIG. 1b, in a schematic manner, in the plane of the electric field.
In FIG. 1a, there is shown three superposed panels, i.e., located in a single plane, designated by P.sub.1, P.sub.2 and P.sub.3. Each of the panels comprises a dielectric support 1 on which parallel wires 2 carrying diodes 3 are disposed. The diode-carrying wires 2 are connected by conductors 7 which are substantially perpendicular to them and are used for controlling the state of the diodes : in each of the panels, all diodes are controlled simultaneously and identically by means of the conductors 7 by voltages sufficient to make them conducting or not. The panels are separated and surrounded by conductive plates which are perpendicular to them and denoted by P.sub.L1, P.sub.L2, P.sub.L3, P.sub.L4.
In FIG. 1b, there is shown a plurality of panels such as P.sub.1, P.sub.2, P.sub.3, denoted here by P, disposed in the channels formed by the plates, denoted here by P.sub.L, taken two by two. The set of panels P in a single channel forms a phase shifter (D.sub.1, D.sub.2, D.sub.3, . . . ). The slack formed by a plurality of phase shifters constitutes an active microwave lens which is illuminated by a source S (FIG. 1a), the latter transmitting an electromagnetic wave whose electric field (or polarization) E is perpendicular to the plates P.sub.L. As an example, there is shown in FIG. 1b the direction of propagation 10 of an incident wave, and a transmitted wave whose direction 20 is deflected with respect to the incident wave.
The panels P being controlled independently of one another, it appears that the phase shift they impart to the wave passing through them can be different from one panel to the next. By joining one behind the other a plurality of panels in a single channel along the path of the microwave, it can be seen that phase shifts from 0 .degree. to 360.degree. can be obtained by increments whose value is related to the number of joined panels. By stacking a plurality of such phase shifters, it is thus possible to implement an electronic scanning in a plane parallel to the electric field E.
Furthermore, in certain applications, it is necessary to be able to have a single antenna operate with two crossed polarizations, i.e., the antenna, or the lens, must be capable of operating with an electromagnetic wave whose electric field is directed along a first given direction, as well as with a wave whose electric field is directed along a direction perpendicular to the preceding one. Such antennas have applications in particular in the fields of antijamming, improvement of target detection and recognition, as well as very-low-altitude flight.